Inhibition of complement deposition on solid-phase bound rabbit aIgG by IVIG II. After coating of the microtiter plates with aIgG, purified C1q was added as a second step, the plates washed, and the inhibition experiments with IVIgM and IVIgG as shown in Fig 1 for C4 and C3 deposition were then performed in 1:200 diluted, C1q-depleted human serum. A representative experiment of three with similar results is shown.